Abstract: A heavy duty pneumatic tire possessing excellent wet-running performances and wear resistance comprises a tread portion provided at its surface with a plurality of main grooves arranged on both sides with respect to an equatorial plane at a given interval in a circumferential direction of the tire and has a negative ratio of not more than 0.3. In this tire, the main grooves curvedly extend in a converging direction from each side end of the tread toward the equatorial plane and terminate on the equatorial plane or in the vicinity thereof within 25% of a tread width (W) centering around the equatorial plane so as to meet the terminals of opposed main grooves with each other or somewhat separate away them from each other and have particular inclination angle (.alpha.), and continuously projection lengths (L.sub.1, L.sub.2) in the widthwise and circumferential directions.

Abstract: A pneumatic tire includes a plurality of blocks, each having a narrow area interposed between one set of two sipes which extend substantially in a transverse direction of the tire and wide areas positioned respectively at both sides of the narrow area across the sipes. An average distance H2 from a tire tread surface of the narrow area to bottom portions of the sipes is less than an average distance H1 from tire tread surfaces of the wide areas to the bottom portions of the sipes. Expanded portions may be provided at the bottom portions of the two sipes. A ratio W2/W1 of a length W2 of the narrow area in the transverse direction of the tire to a length W1 of the wide areas in the transverse direction of the tire may satisfy 0.50.ltoreq.W2/W1.ltoreq.0.95. A length, in the circumferential direction of the tire, of at least one side end portion of the narrow area may be longer than a length, in the circumferential direction of the tire, of a central portion of the narrow area.

Abstract: A pneumatic tire manufactured with a sector mold including of plural arc-shaped segments each having plural island rows of ribs or blocks in its tread portion and sipes formed in at least one island row. Among these sipes, a depth of a sipe located in the vicinity of a position of a tread surface corresponding to an edge of the arc-shaped segment is made shallower than that of a sipe located at a position other than the above position.